BLOOMINGTON – Fire investigators arrested an 18-year-old Bloomington High School student Wednesday, alleging he started a May 21 fire that gutted the school’s administration building.

The investigators interrupted a summer session class at the high school about 10 a.m. and arrested Jovanny Lua, who was attending.

He was arrested on suspicion of arson and burglary, said Mike Horton, deputy fire marshal for the San Bernardino County Fire Department.

Lua was taken from the high school to the Sheriff’s Fontana substation, where investigators interviewed him. He was booked at West Valley Detention Center in Rancho Cucamonga. His bail was set at $125,000.

No one was injured but the blaze caused more than $400,000 in damage.

And the effects of the fire will likely continue through the 2011-12 school year, said Roger Kowalski, member of the Colton Unified School District’s Board of Education.

“It was a horrible thing,” Kowalski said. “An entire school will be disrupted for, my guess, a year.”

The fire displaced about 35 staffers, who were forced to set up in whatever available space they could find on campus. It also disabled the school’s bell, Internet, and communication systems, district officials said in May.

In June, Principal Ignacio Cabrera used a golf cart and megaphone to usher students off to their classes.

Since then, crews have cleaned out what’s left of the building, Kowalski said. Construction on a new administrative building has not yet begun.

“It might take a while,” Kowalski said.

Kowalski commended investigators and praised Bloomington High School students, who he said retained their focus despite the fire.

And no teacher would want their students “resorting to an act like that,” he said, referring to the alleged arson.

“It’s just a shame that somebody thought that’s how they should resolve something or deal with something,” he said. “I don’t understand the motive behind that.”